This invention relates to a modular fluid control apparatus responsive to pneumatic input signals for developing pneumatic output control and operating signals and to a method of making the modular control apparatus for a fluid control system and particularly to such a modular fluid control apparatus specially adapted for controlling the conditioning of environmental air supplied to a building enclosure.
Control systems responsive to various input signals and developing controlling and operating signals are used in various industrial applications. Although such systems generally use electrical and electronic circuits and components, fluid control systems have been developed and advantageously used in various applications. Electronic control systems which have been developed may use various circuit board approaches. Fluid control systems also have been widely used in industrial type controls and have also been particularly applied to heating, ventilating and air conditioning control systems wherein pneumatic signals are generated for controlling the temperature and humidity of air supplied to building enclosures. Such systems have been particularly applied to institutional, commercial and industrial applications where relatively complex control systems are required. A particularly satisfactory conditioning control system uses a constant air flow through the system with controlled introduction of fresh air and exhaust of stale air in combination with a means for heating, cooling and humidifying the air prior to supply to the conditioned zone or zones of an enclosure. The simplest system provides continuous introduction of outside air with 100% exhausting of return air. A mixed air system is advantageously used to reduce the energy consumption. In mixed air systems, a portion of the exhaust air is returned to the supply with selective varying of the volume of return air, generally depending upon the relative energy content state of the outside and return air. In all such systems separate heating, cooling and/or humidification units are mounted in the zone supply duct or passageway. The duct includes an outdoor air input and in the mixed air systems a return air input connected to the outlet duct upstream of an exhaust air duct. Damper units are provided in the outdoor air duct, the exhaust duct and the return duct for selectively controlling the mixture of air supplied to the conditioned zone. The design of the control systems may be relatively complex when applied to multiple building or a large building complex. The necessity for sophisticated control systems has been intensified by the energy crisis. The custom design of such sophisticated systems requires skilled personnel having a broad knowledge of the various components and subsystems available. Pneumatic control systems have been and are individually designed and constructed with the various signals interconnected through special circuit design to provide the desired functional control. It is this interaction within the circuit which particularly is effected by the broad knowledge and the level of technical skill of the designer as well as an intimate knowledge of the installation. Although the various standard input/output control and modifying components are well known, the circuit design using such components and the circuit connection is a difficult and time consuming process as the complexity of the systems increases. A custom design therefore is not only expensive but is subject to the technical ability of the field personnel involved in selling and designing of heating, ventilating and air conditioning systems. For example, the outdoor air control normally is based on the relative condition of the outdoor air and the return air as well as the interrelationship of various zone signals and the like and operates to control a position of the several dampers. For example, it might be desired to provide natural cooling whenever the outdoor air contains less energy than the return air. Minimum ventilating may be required even when the outdoor air energy is greater than the return air. The system must also consider the damaging effect which can occur if abnormally low temperature air is introduced into the system which may cause component freeze-up. These and similar interrelated controls are required in most sophisticated mixed air systems for heating, ventilating and air conditioning of air. Many other basic functional factors must also be considered in the design of the system for operating the dampers, the heating means, the cooling means and the humidifying means depending upon the requirements specified for the air supplied to the conditioned zone.
Further, the field installation with the required system interconnections present a further source of possible error in the construction of the system.
There has been and is a very significant need for some method of simplification in the designing and construction of pneumatic control systems but the system components have not been integrated into an appropriate modular system, such as in electronic systems.